1. Field of the Invention
The present invention relates to an endoscopic channel switching device which switches the communication states of channel portions in an endoscope, an endoscope, and a manufacturing method of an endoscopic channel switching device.
2. Description of the Related Art
Generally, an endoscope has an observation window for observation in a body cavity. The field of view of the observation window narrows when, for example, body fluid sticks to the observation window. Thus, the endoscope requires the supply of at least one of air and water to the observation window to ensure the field of view. The endoscope has a switching device for switching from one of the air supply and water supply to the other. The switching device has a piston and a cylinder. The piston moves relative to the cylinder, so that one of the air supply and water supply is switched to the other.
Such endoscopes have been disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 9-122069 and Jpn. Pat. Appln. KOKAI Publication No. 59-11828. In Jpn. Pat. Appln. KOKAI Publication No. 9-122069 and Jpn. Pat. Appln. KOKAI Publication No. 59-11828, a piston moves relative to a cylinder, so that one of air supply and water supply is switched to the other.
In Jpn. Pat. Appln. KOKAI Publication No. 9-122069 and Jpn. Pat. Appln. KOKAI Publication No. 59-11828, the cylinder has a diametrically increased portion which is provided in the lower part of the cylinder and which has an inside diameter larger than the minimum inside diameter of the cylinder. That is, the inside diameter of the lower part of the cylinder is larger than the minimum inside diameter of the cylinder. In other words, the whole lower part of the cylinder is bulging in the diametrical direction of the cylinder.
In the diametrically increased portion, a hole portion is provided in the circumferential surface of the cylinder. An end portion of a channel portion is provided inside the cylinder through the hole portion. This channel portion is coupled to the cylinder, for example, by welding. Since the diametrically increased portion is provided, a coupling part between the channel portion and the cylinder is provided outside the thinnest portion of the cylinder in the diametrical direction of the cylinder.
The end portion of the channel portion is inserted in the cylinder. Thus, in this end portion, a part inserted in the cylinder is cut and removed by a tool. The coupling part has an uneven surface formed by welding. This uneven surface is also cut and removed by the tool as a finishing process.